Method for driving a plasma display panel

ABSTRACT

The present invention discloses a method for writing information on a plasma display panel with the minimum write voltage. In the plasma display panel, an upper member and a lower member face each other, sandwiching a gap filled with gas therebetween, and the upper member had column electrodes covered with a dielectric layer and the lower member has row electrodes covered with a dielectric layer, and the upper and the lower members are not similar in construction and/or in the material of which they are made. In one embodiment, when a secondary electron radiation emissivity of the surface of the dielectric layer of row electrodes which are provided on the lower member is higher than a secondary electron radiation emissivity of the surface of the dielectric layer of column electrodes which are provided on the upper member, a write voltage is supplied to selected electrodes with a polarity such that the row electrodes become negative and the row electrodes become positive.

United States Patent [191 Andoh et al.

[451 July s, 1975 METHOD FOR DRIVING A PLASMA DISPLAY PANEL [75] Inventors: Shizuo Andoh, Kobe; Kenji Murase; Toshiaki Iemori, both of Kakogawa; Hiroshi Yamamoto, Ashiya; Norihiko Nakayama, Kobe, all of Japan [73] Assignee: Fujitsu Limited, Japan [22] Filed: Dec. 19, 1973 [21] Appl. No.: 426,020

[30] Foreign Application Priority Data Primary Examiner--R. V. Rolinec Assistant Examiner-Lawrence J. 'Dahl Attorney, Agent, or FirmMaleson, Kimmelman and Ratner [5 7] ABSTRACT The present invention discloses a method for writing information on a plasma display panel with the minimum write voltage. In the plasma display panel, an

upper member and a lower member face each other, sandwiching a gap filled with gas therebetween, and

' the upper member had column electrodes covered with a dielectric layer and the lower member has row electrodes covered with a dielectric layer, and the upper and the lower members are not similar in construction and/or in the material of which they are made. In one embodiment, when a secondary electron radiation emissivity of the surface of the dielectric layer of row electrodes which are provided on the lower member is higher than a secondary electron radiation emissivity of the surface of the dielectric layer of column electrodes which are provided on the upper member, a write voltage is supplied to selected electrodes with a polarity such that the row electrodes become negative and the row electrodes become posi- IIVe.

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' DISCHARGELI L 1| POINT 1 METHOD FOR DRIVING A PLASMA DISPLAY PANEL BACKGROUND OF THE INVENTION The present invention relates to a method for driving a plasma display panel in which an upper member and a lower member face each other sandwiching a gap filled with gas therebetween. Said upper and lower member are similar neither in construction nor in the materials of which they are made.

As is well known, in the plasma display panel, two insulated base plates, that is, an upper member and a lower member, are each provided with a plurality of parallel electrodes which are covered by a dielectric layer. Said upper and lower members face each other in such a manner that the electrodes on upper member and the electrodes on lower member cross each other and a gap filled with ionizable gas exists therebetween. In the above-mentioned construction, a plurality of discharge points crossing the gas filled with gas at the crossing points of electrodes an upper member (column electrode) and electrodes on lower member (row electrodes) are formed in the form of a matrix. After discharge point is fired, said fired discharge point has a inherent memory due to a wall charge which adheres to the surface of the dielectric layer.

In the usual method of driving the above-mentioned plasma display panel, while an alternate sustaining voltage is supplied between row electrodes provided on one base plate and column electrodes provided on the other base plate, a write voltage which exceeds the discharge voltage is supplied between selected row and column electrodes. As a result of this, a discharge is produced at the cross point of said selected row and column electrodes and said discharge is maintained by the alternate sustaining voltage until an erase voltage is supplied between said selected row and column electrodes. In this case, in plasma display panel wherein the upper member and the lower member face each other sandwichings a gap filled with gas, and are constituted symmetrically in their constructions and in their materials, a polarity of the write voltage for the selected row and column electrodes does not affect to the discharge effect which is produced cross the gap filled with gas. That is, the absolute value of the writing voltage is independent of the polarity of the voltage applied to these electrodes.

Recent developments in this technical field have provided a plasma display panel in which the upper member and the lower member which face each other sandwiching a gap filled with gas therebetween, are similar neither in construction or in the material of which they are made. For example, in the plasma display panel in g which fluorescent material is added on one dielectric layer for the purpose of changing the discharging color from one color to another, the construction of side of column electrodes and the construction of side of row electrodes become unsimilar. Another example is prO- posed such as that the construction and the thickness of the dielectric layer which covers the column electrodes is different from that of the dielectric layer which cover the row electrodes. Further, a plasma display panel for special pattern display now exists in which the pitches and widths of the column electrodes are different from those of the row electrodes. In the abovementioned plasma display panel in which the upper member and the lower member are not similar in construction, the inventors of the present invention found that, in the case of driving such type plasma display panel, the value of the voltage which is necessary for the write operation depends on the polarity of the write voltage.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of driving a plasma display panel whose upper and lower members are not similar in construction and in material by utilizing a minimized write voltage.

Another object of the present invention is to provide a method for decreasing the write voltage which is the highest voltage for driving the plasma display panel; among the write voltage, the erase voltage and the sustaining voltage and for decreasing an electricl power dissipated in the driving circuit.

Simply speaking, the concept of the present invention is based on the recognition that when the construction or the material of the dielectric layer covering the column electrodes is different from those of the dielectric layer covering the row electrodes the surfaces of these dielectric layers contacting the gas have different secondary electron radiation emissivities. In this specification, the technical term dielectric layer includes both one layer and multi-layers and is used to mean entire or partial layers which directly or indirectly cover the electrodes without relation to the function of each layer. For the plasma display panel, which provides above-mentioned construction the write voltage is applied to the Ielectrodes which are covered by a dielectric layer having ansurface of higher secondary electron radiation emissivity with negative polarity and the electrodes which are covered by a dielectric layer having a surface of lower secondary electron radiation emissivity with positive polarity. When the pitches or the widths of the column electrodes and the row electrodes are different, the distribution of the electric fields on the surfaces of the dielectric layer covering the column electrodes is different from that covering the row electrodes. Consequently, the electrodes where the electric fields are more concentrated are selected as negative polarity of the write voltage and the electrodes where the electric fields are less concentrated are selected as positive polarity of the write voltage.

Further features and advantages of the present invention will be apparent from the ensuing description with reference to the accompanying drawings to which, however, the scope of the invention is in no way limited.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of an essential portion of a plasma display panel;

FIGS. 2A, 2B and 2C are block and schematic diagrams of the driving circuit of the plasma display panel according to the present invention;

FIGS. 3A and 3B are waveforms explaining the method of applying the write voltage to the plasma display panel shown in FIG. 2A;

FIG. 4 is waveforms explaining another method of applying the write voltage to the plasma display panel shown in FIG. 2A.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is very effective to the plasma display panel wherein the upper memberand the lower member are not similar in construction and in material. Such plasma display panel can be divided into two categories, that is: (l) the construction or the material of the dielectric layers which are provided onthe two members is different; (II) the construction of the electrodes which are provided on the two members is different. l I

The following types belong to the above-mentioned category (I). a. A type which provides fluorescent material on onedielectric layer for the purpose of changing the gas discharging color. b. A type which constitutes one dielectric layer with opaque or darkened material andthe other dielectric layer with transparent material for thepurpose of increasing the contrast of the display panel. c. A type which provides a protecting layer or a second layer on one of the dielectric layers forthe purposeof protecting said dielectric layer from ion bombardment. d. A type. which provides dielectric layers having different thickness for the purpose of obtaining memory of different amounts of wall charges on the each dielectric layer.

The following types belong to the above-mentioned category II. e. A type in which the width of one electrodes is larger than that of the other electrodes for the purpose of displaying a special pattern, for example, lines. f. A type in which the pitch of one electrodes is larger than that of the other electrodes for the purpose of displaying characters having special type form.

FIG. 1 shows a sectional view of an essential portion of the plasma display panel which belongs to type (a) above. This plasma display panel comprises an upper side member and a lower side member 20 which face each other sandwiching a discharging gap filled with gas therebetween. The main part of the upper side member 10 is constituted with a transparent and insulated base plate 11 and a plurality of column electrodes 12 are provided in parallel on the base plate 11. Said column electrodes 12 are covered with a dielectric layer 13, such as a low melting temperature glass. The main part of the lower side member is constituted with a transparent and insulated base plate 21 and a plurality of row electrodes 22 are provided in parallel on the base plate 21. Said row electrodes 22 are covered with a dielectric layer 23. The above-mentioned column electrodes 12 and row electrodes 22 are crossed at right angles to each other, and discharge points which cross the discharging gap 15 are constituted at the crosspoints of the column electrodes and the row electrodes. The important point of the embodiment is that a fluorescent material 14 is applied on the dielectric layer 14 of the upper side member 10.

When the plasma display panel which is constructed above is driven, a write voltage is supplied with a polarity such that the row electrodes 12 of the upper memher are of positive polarity that is, of relatively high potential, and the column electrodes 22 of the lower member are negative polarity, that is, of relatively low potential.

FIG. 2A shows a block diagram for driving such a plasma display panel as shown in FIG. 1. Each column electrode 12-1, 12-2 12-n and each row electrode 22-1, 22-2 22-n, provided in the plasma display panel 30, are connected via respective coupling condensers C to a common sustaining voltage source 31. The common sustaining voltage source 31 supplied sustaining pulses V alternately to said column electrodes column electrode and rowelectrode is connected via respective resistors R to column address circuit 32 and row address circuit 33. The row address circuit and the column address circuit 33 include an individual drivers for each of the column and row electrodes and supply in accordance with an information signal from a control circuit 34 a write voltage or anerase voltage to the column and row electrodes which are selected. A driver which is included in the column address circuit 32 is represented by a transistorv Q as shown in FIG. 2B. Transistor Q supplies a positive voltage V equal to the sustaining voltage level V, as one portion of the write voltage to the column electrode 12-1 covered with the dielectric layer to which the fluorescent material is applied. A driver which is included in the row address circuit ,33 is represented by a transistor Q as shown in.FIG. 2C. The transistor Q supplies a negative .the row electrode 22-1 becomes the negative potential V,,- Therefore, a write voltage v u'r'l' l u'n VW] is applied to the discharge point at the crosspoint of the selected rowelectrode and selected column electrode.

When said write voltage exceeds the discharge voltage, the selected discharge point is fired at the abovementioned crosspoint.

. According to an experiment conducted by the inventors, in the plasma display panel to which the fluorescent material is applied as shown in FIG. 1, the write voltage V which has a polarity as described in the above-mentioned embodiment was 270 volts. That is, a satisfactory write operation is effected by applying a positive 170 volts which is equal to the sustaining voltage, to the selected column electrode and by applying a negative volts to ,the selected row electrode. However, in the same plasma display panel, when the polarity of said write voltage is reversed as shown in.

(1), (2) and (3) of FIG. 3B, that is, when the write operation is effected with a polarity such that the abovementioned row electrode is negative, a write voltage V of 340 volts was required between the column electrode and row electrode. This means that the amount of the write voltage can be decreased about 20% by selecting the polarity of said write voltage.

The fact that the amount of the write voltage in the plasma display panel as shown in FIG. 1 depends on the polarity of the write voltage is due to the difference in the secondary electron radiation emissivity on the surfaces of the dielectric layers of the upper member and the lower mem er, When a negative potential is 511px plied to one electrode covered with a dielectric layer f layer having high secondary electron-radiation emissivity are attracted by the positive potential of the opposite electrode and pass through the gap filled with. gas repeat the collision with gas molecules and effectively excite said gas molecules. However ,-when a positive potential is supplied to one electrode covered with a dielectric layer having high secondary electron radiation emissivity, and a negative potential is supplied to the other electrode covered with a dielectric. layer having low secondary electron radiation emissivity, secondary electron which are radiated from the surface of the dielectric layer having. high secor dary'electron radiation emissivity are put back by the 'negative potential of, the opposite electrode without contributing the excitation of the gas molecules. l

We assume that a relation yc yr exists between the secondary electron emissivities 7c and yr on the surface of the dielectric layer of the upper member of column electrodes and the lower member ofrow electrodes.

' We represent the write voltages V and Vt} as shown belong.

V a write voltage which has a polarity such that the column electrode is relatively high potential, that is, a write voltage which has a relation V V 0;

V a write voltage which has a polarity such that the column electrode is relatively of low potential, that is. a write voltage which has a relation V V 0.

The following relation exists between abovementioned two write voltages V and V V V In the plasma display panel shown in FIG. 1, the dielectric layer 23, composed of low melting temperature glass, provided on the lower member has a secondary electron radiation emissivity higher than that of the fluorescent material 14 provided on the upper member 10. Therefore, it is recommended that a write voltage be utilized which has a polarity such that the column electrodes become of positive polarity. In the driving of the plasma display panels which belong to the above-mentioned types (b) and (c), included the category (I), the write voltage which has the polarity I such that the electrodes covered with the dielectric layer having high secondary electron radiation emissivity is positive potential is utilized.

When the arrangement of the row electrodes is not similar to that of the column electrodes, the write voltage depends on its polarity. This is due to the fact that the densities of the electrical fields on the surfaces of the dielectric layers are different. As shown with broken lines in FIG. 2A, when the widths of the column electrodes 12-1, 12-2, 12-3 I2-n are larger than those of the row electrodes 22-1, 22-2 22-n, the density of the electric lines of force on the surface of the dielectric layer which covers the row electrodes of narrow width is higher than that of the dielectric layer which covers the row electrodes having a width wider than that of the column electrodes. Therefore, when the row electrodes are actuated with negative polarity, secondary electrons having high energy can be radiated by strong ion bombardment from the surface of the dielectric layer and the writing operation can be effected by a minimum voltage. Therefore, with respect to the type (F), above plasma display panel having different electrode pitches is driven by a write voltage having a polarity such that the electrodes having narrower width is negative polarity. With respect to the type (d) above, plasma display panel having dielectric layers with different thickness is driven by a write voltage having a polarity such thatthe electrodes which are covered by the dielectric layer having thin thickness is negative polarity, because, the electric. field is more concentrated to the surface of, the dielectriclayer having thin thickhatched portions in-(1) and,(2) of FIG. 4 are supplied to the electrodes which-are selected. Then, at the dis charge points which are selected, the voltage'which is superposedto the sustaining voltage V and the write voltage V as shown in (3) of FIG. .4, is supplied with the polarity such that the column electrodes covered by the dielectric layer which'has fluorescent materialapplied and has low secondary electron emissivity are of relatively higher potential than the row electrodes. It is clear from the above-mentioned explanation that in the method using the write voltage shown in FIG. 4, the write operation can be effected with minimized write voltage.

As is clear from the above-mentioned explanation of the present invention, the driving of the plasma display panel whose upper member and lower members are not similar in construction or in material can be carried out with a low write voltage. Decreasing the write voltage which is required the most high voltage is very effective to decrease electrical power dissipation of the transistors and another circuit elements and the driving circuit for the plasma display panel can be constructed at low cost.

While the invention has been particularly shown and described with reference to preferred embodiment thereof, it will be understood by those skilled in art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. A method of driving a plasma display panel which includes a first member and a second member which are provided facing each other via a gap filled with ionizable gas, said first member providing a plurality of first electrodes which are covered with a first dielectric layer having a first surface contacting said ionizable gas, said second member providing a plurality of second electrodes which are covered with a second dielectric layer having a second surface contacting said ionizable gas, said second surface having secondary electron radiation emissivity higher than that of said first surface, and said first electrodes being provided in a direction which crosses said second electrodes,

said method of driving said plasma display panel comprising the steps of applying an alternating sustaining voltage between said first electrodes and said second electrodes, applying a write voltage between electrodes which are selected from said first electrodes and electrodes which are selected from said second electrodes having a polarity such that said second electrodes covered with said second dielectric layer having a surface of higher secondary electron emissivity have a negative polarity and said first electrodes covered with said first dielectric layer having a surface of lower secondary electron emissivity have a positive polarity,

thereby producing a discharge at the crosspoint of said first electrodes and said second electrodes across said gap filled with ionizable gas.

2. The method of driving a plasma display panel according to claim 1 which further comprises,

applying said write voltage at the same time as said alternating sustaining voltage.

3. A method of driving a plasma display panel construction which includes a first member and a second member which are provided facing each other via a gap filled with ionizable gas, said first member providing a plurality of first electrodes which are covered with a first dielectric layer having a first surface contacting said ionizable gas, said second member providing a plurality of second electrodes which are covered with a second dielectric layer having a second surface contacting said ionizable gas, said first electrodes being provided in a direction which crosses said second electrodes,

said method of driving said plasma display panel comprising the steps of applying an alternating sustaining voltage between said first electrodes and said second electrodes, forming said first and second electrodes for concentrating the electric field crossing said gap filled with ionizable gas at a higher density on said second surface of said second dielectric layer with respect to said first surface of said first dielectric layer, applying a write voltage between electrodes which are selected from said first electrodes and elec-' trodes which are selected from said second electrodes with a polarity such that said second electrodes have a negative polarity and said first electrodes have a positive polarity, thereby producing a discharge at the crosspoint of said first electrodes and said second electrodes across said gap filled with ionizable gas. 

1. A method of driving a plasma display panel which includes a first member and a second member which are provided facing each other via a gap filled with ionizable gas, said first member providing a plurality of first electrodes which are covered with a first dielectric layer having a first surface contacting said ionizable gas, said second member providing a plurality of second electrodes which are covered with a second dielectric layer having a second surface contacting said ionizable gas, said second surface having secondary electron radiation emissivity higher than that of said first surface, and said first electrodes being provided in a direction which crosses said second electrodes, said method of driving said plasma display panel comprising the steps of applying an alternating sustaining voltage between said first electrodes and said second electrodes, applying a write voltage between electrodes which are selected from said first electrodes and electrodes which are selected from said second electrodes having a polarity such that said second electrodes covered with said second dielectric layer having a surface of higher secondary electron emissivity have a negative polarity and said first electrodes covered with said first dielectric layer having a surface of lower secondary electron emissivity have a positive polarity, thereby producing a discharge at the crosspoint of said first electrodes and said second electrodes across said gap filled with ionizable gas.
 2. The method of driving a plasma display panel according to claim 1 which further comprises, applying said write voltage at the same time as said alternating sustaining voltage.
 3. A method of driving a plasma display panel construction which includes a first member and a second member which are provided facing each other via a gap filled with ionizable gas, said first member providing a plurality of first electrodes which are covered with a first dielectric layer having a first surface contacting said ionizable gas, said second member providing a plurality of second electrodes which are covered with a second dielectric layer having a second surface contacting said ionizable gas, said first electrodes being provided in a direction which crosses said second electrodes, said method of driving said plasma display panel comprising the steps of applying an alternating sustaining voltage between said first electrodes and said second electrodes, forming said first and second electrodes for concentrating the electric field crossing said gap filled with ionizable gas at a higher dEnsity on said second surface of said second dielectric layer with respect to said first surface of said first dielectric layer, applying a write voltage between electrodes which are selected from said first electrodes and electrodes which are selected from said second electrodes with a polarity such that said second electrodes have a negative polarity and said first electrodes have a positive polarity, thereby producing a discharge at the crosspoint of said first electrodes and said second electrodes across said gap filled with ionizable gas. 